Water purification device

ABSTRACT

A water purification and/or desalination plant for producing drinking water from a polluted water source or sea water with the aid of sunlight, which plant includes an evaporator ( 1 ) having a roof part ( 2 ) made of a light-penetrable material, and an underlying basin part ( 3 ) containing the water that is to be purified, which basin part ( 3 ) includes channels ( 17 ) for collecting water vapor that has been condensed on the inside of the roof part ( 2 ), and a reservoir ( 10 ) for purified water. The plant also includes a device for removing moist air or vapor from the evaporator and a device for condensation of the moist air or vapor outside the evaporator.

CROSS REFERENCE TO RELATED APPLICATION

The present application is the national stage under 35 U.S.C. 371 ofPCT/NO98/00039, filed Feb. 4, 1998.

FIELD OF THE INVENTION

The present invention relates to a water purification and/ordesalination plant for producing water from a polluted water source orsea water with the aid of sunlight, which plant includes an evaporatorhaving a roof part consisting of a light-penetrable material, and anunderlying basin part containing the water that is to be purified, whichbasin part includes means for collecting water vapor that has beencondensed on the inside of the roof part, and a reservoir for purifiedwater.

BACKGROUND OF THE INVENTION

In large parts of the world the fresh water resources are limited anddrinking water therefore has to be produced from brackish water or seawater. The most common water purification plants areevaporation/condensation processes in which the requisite energy isproduced by burning cheap natural gas (in the Gulf region) or morecommonly, by harnessing solar energy. In many regions there is a greatneed for simple, efficient and low-cost equipment for the desalinationof sea water.

A number of such plants and devices for desalination and purification ofdrinking water which employ solar energy are previously known.

DE 2503251 makes known a device for producing drinking water frompolluted or saline water with the aid of solar energy. This evaporatorconsists of a basin with a roof in the form of an inverted V, which canbe penetrated by solar energy. In the lower end of the inclined roofthere is a run-off channel which receives water that has condensed onthe inside of the roof.

DE 3501396 A describes a similar device having a basin and a glass roofin the form of an inverted V. In the lower end of the roof there is acollecting channel for water which has condensed on the inside of theroof.

DE 2650482 describes a device consisting of a basin and a sloping glassroof, wherein the glass roof is cooled in order to enhance thecondensation.

International Patent Application WO 91/04228 makes known a method anddevice for producing drinking water from polluted water with the aid ofsolar energy, consisting of a construction having a plurality ofchambers or sections, of which one chamber or section is an evaporationchamber and a second section is a condensation chamber. SwedishPublished Patent Application 46213 makes known a transportable devicefor producing fresh water by desalting sea water with the aid of solarenergy. The device includes a casing having at least one transparentportion and a collecting channel for fresh water. In the bottom of thedevice there is provided a solar energy absorber having ducts forcooling the absorber with the aid of a coolant. The coolant flows in aclosed circuit and is used to heat the incoming sea water.

U.S. Pat. No. 4,187,151 describes a floating desalination plant. Abottom having a preferably transparent or translucent chamber floats onthe surface of the sea. Waves cause the chamber to expand and contractso that air is drawn into the chamber. The moist air exiting the chamberis conducted to a condensation and collecting tank below the seasurface.

There are also known a number of devices which use reverse osmosis forproducing fresh water from sea water. As examples of publications whichdescribe this, reference may be made to U.S. Pat. Nos. 4,076,626,4,452,696 and 4,770,775.

One disadvantage of the known devices is that they are relatively bulkyand relatively stringent requirements must be met with respect toperiodic maintenance.

Another disadvantage of these known devices is that they are relativelyinefficient, since most of the solutions are based on a more or lessclosed chamber, where the water vapor is condensed on the surface of thechamber.

SUMMARY OF THE INVENTION

One of the objects of the present invention is to provide a plant of theaforementioned type that is so inexpensive, efficient and simple that itcan be used in small communities along the coast in sunny developingcountries, e.g., along the coast of the south-eastern Mediterranean orthe Red Sea.

Another object of the present invention is to provide a plant of theaforementioned type, where its efficiency is substantially improved,compared with other known plants.

Yet another object of the invention is to provide a plant of the saidtype, where the necessity of inspection and periodic maintenance isminimal.

This is accomplished with a water purification and/or desalination plantfor producing drinking water from a polluted water source or sea waterwith the aid of sunlight, which plant includes an evaporator having aroof part consisting of a light-penetrable material, and an underlyingbasin part containing the water that is to be purified, which basin partincludes means for collecting water vapor that has been condensed on theinside of the roof part, and a reservoir for purified water, whichaccording to the invention is characterized in that the plant alsoincludes means for removing moist air or vapor from the evaporator andmeans for condensation of the moist air or vapor outside the evaporator.

The means for removing moist air or vapor from the evaporator andcondensation thereof preferably include a condenser connected to a fan.

In the basin part there is preferably provided means for increasing theabsorption of heat, which means includes a plate-shaped body which iskept at a constant distance from the surface of the water in the basinpart with the aid of buoyancy bodies or floats, which plate-shaped bodyhas a dark, heat-absorbent surface and includes a thermal insulationmaterial.

The plate-shaped body preferably has a surface that is smaller than thesurface of the basin part, or the plate-shaped body is equipped withholes or slots for the circulation of water from the underside of theplate-shaped body to the upper side thereof.

The evaporator is connected by means of a pump to a supply of waterwhich is to be purified, which pump is connected to level sensors in thebasin part of the evaporator unit for controlling the water level in thebasin part.

The roof part of the evaporator consists of a light-penetrable material,which material is preferably heat-insulating, and which material ispreferably coated with a tear-resistant coating.

The plant preferably includes a solar panel for producing electric powerfor the fan, the pump and optionally the condenser.

The invention will be described in more detail below with the aid ofexemplary embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified outline of a desalination and water purificationplant according to the invention.

FIG. 2 is a section of the plant according to FIG. 1.

FIG. 3 is a block diagram showing the different units in the plant.

FIG. 4 shows an example of the interconnection of a plurality ofdesalination and water purification plants.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a plant for desalination and purification of water. Theplant consists of an evaporator unit 1, consisting of a housing with atranslucent or transparent roof part 2 and a basin part 3. The roof part2 may, e.g., consist of so-called channeled sheets, which give goodinsulation. Optionally, a surface layer of a tear-resistant material maybe applied to the roof part 2. The unit 1 is connected to a water supply4, e.g., groundwater or sea water, which is connected to the evaporatorunit 1 via a pump 5 and supply pipes 6. Furthermore, the plant consistsof a condenser 8 connected to the evaporator unit 1 via vapor dischargepipes 7, a fan 9 connected to the condenser 8 and a reservoir 10 forpurified water connected to the condenser. From the fan 9, supply pipes11 run back to the evaporator unit 1.

FIG. 2 shows a section through an evaporator unit 1. The evaporator unit1 consists of a roof part 2 having a sloping or inverted V-shapedprofile, a basin part 3, which, e.g., is designed to be rectangular withuptight walls. Water collecting channels 17 are provided in thetransition between the roof part 2 and the basin part 3. The bottom ofthe basin part 3 is filled with water 12. Under the surface 13 of thewater there is provided a plate-shaped body 14 which, with the aid ofbuoyancy bodies or floats 15, is located at a certain distance from thewater surface. The purpose of the plate-shaped body 14 will be explainedlater. Furthermore, the evaporator unit 1 is provided with a vaporoutlet 18 and a water inlet 19. To allow control of the water level inthe basin part 3 there are provided two level sensors 16 and 16′ whichare located at respectively the highest and lowest allowed water levelsin the basin part.

The plate-shaped body 14 consists of a light and heat absorbent materialand is provided with holes or slots which allow water circulation fromthe underside to the upper side of the body 14. Optionally, the placemay be dense and be smaller in size than the basin part 3, so that thewater can flow up along the sides of the plate. If the plate 14 is toattain a maximum heat absorption, it may, e.g., be made of black ordark, insulating material. When the sun shines on the evaporator unit 1,the plate-shaped body 14 will absorb heat, and emit this heat into thewater which is above the body 14. This water will then have a highertemperature than the water below the body 14. The use of a plate-shapedbody 14 of this kind will mean that the evaporation will take place morerapidly than in a similar plant which does not use a plate-shaped lightand heat absorbing body. The water above the plate-shaped body 14 willbeing to evaporate and rise in the space above the surface 13 of thewater. When the vapor strikes the roof part 2, some of the water will becondensed and run down along the roof part 2 and be collected in thewater collecting channels 17. From the channels 17, the condensed wateris led out of the evaporator unit 1. In addition to condensed water,some of the vapor-containing air in the space above the water surface 13will be led out of the evaporator unit 1. When the water level in thebasin part 3 falls below a certain level, the lower level sensor willgive a signal to the pump 5 (FIG. 1), which begins to pump untreatedwater into the basin part 3 until the water level reaches the upperlevel sensor 16. This sensor 16 will then send a signal to the pump 5,which stops.

FIG. 3 is a block diagram showing the connection of the various units.The pump 5 is connected to a water source 4, e.g., a groundwater source,sea water or other impure water. The pump 5 is connected to theevaporator unit 1 via a supply pipe 6.

The condensed water collected in the water collecting channels 17 (FIG.2) is conducted via the pipe 19 directly to the water reservoir 10. Thiswater reservoir 10 may, e.g., be a tank buried in the ground in order tominimise evaporation therefrom.

The moist air or vapor that is collected in the evaporator unit 1, ispassed via the pipe 7 to a condenser 8. This task of this condenser 8 isto condense water from the moist air. From the condenser 8, a pipe 21conducts water to the water reservoir 10, whilst a pipe 20 conducts airfrom the condenser 8 to a fan 9. The purpose of conducting air back tothe evaporator unit 1 is to prevent dust and particles from outside frombeing collected in the evaporator unit 1, and also that this air, whichhas been cooled in the condenser 8, will result in a cooling of the roofpart 2 (FIG. 2) of the evaporator unit 1 and thereby further improveefficiency. From the fan 9, a pipe 11 conducts air back to theevaporator unit 1.

The fan 9, the pump 5 and the condenser 8 may be operated by means ofelectricity. If an electricity supply is not available, the energyrequired can be produced with the aid of a solar panel 22, optionally incombination with rechargeable batteries. The condenser 8 and the fan 9are connected to the solar panel 22 by an electric conductor 23. Thelevel sensors or switches 16, 16′ (FIG. 2) are connected to the solarpanel 22 by an electric conductor 24. A electric conductor 26 runs fromthe level sensors or switches 16, 16′ to the pump 5.

The use of a solar cell 22 allows the plant to be fully self-sufficientas regards energy and thus in no need of a connection to other sourcesof energy.

FIG. 4 shows an embodiment of the plant according to the inventionconsisting of three evaporator units 1, 1′, 1″ connected in parallelrelation. The arrangement and connection of the evaporator units 1, 1′,1″, the pump 5, the fan 9 and the condenser 8 are the same as shown inFIG. 3. In order to be able to selectively control the supply of waterfrom the pump 5 to the individual evaporator units, there must inaddition be provided the necessary valve equipment and/or control units(not shown).

Of course, electricity supplies other than a solar panel 22 may be usedfor operation and regulation of the plant. If the plant, e.g., is in thevicinity of flowing water, a water-operated power turbine could be usedto produce the necessary electric power. Optionally, the condenser 8 maybe water-cooled instead of operated by electricity.

What is claimed is:
 1. A water purification and/or desalination plantfor producing drinking water from a polluted water source or sea waterwith the aid of sunlight comprising: an evaporator unit (1) having aroof part (2) consisting of a light-penetrable material an underlyingbasin part (3) containing water (12) that is to be purified; which basinpart (3) includes means (17) for collecting water that has beencondensed on the inside of the roof part (2) and a reservoir (10) forpurified water unit, means for removing moist air or vapor from theevaporator, and means for condensing the moist air or vapor outside theevaporator unit; wherein the basin part (3) further includes means forincreasing the absorption of heat, said means for increasing theabsorption of heat comprising a plate-shaped body (14) and buoyancybodies or floats (15) which maintain the plate-shaped body a constantdistance from a surface (13) of the water (12) in the basin part; whichplate-shaped body has a dark, heat-absorbent surface and includes athermal insulation material.
 2. The water purification and/ordesalination plant according to claim 1 wherein the means for removingthe moist air or vapor from the evaporator unit include a condenser (8)connected to a fan (9).
 3. The water purification and/or desalinationplant according to claim 2 wherein the evaporator unit (1) is connectedby means of a pump (5) to a supply of water (4) that is to be purified,which pump (5) is connected to level sensors (16, 16′) in the basin part(3) of the evaporator unit (1) for regulating the water level in thebasin part (3).
 4. The water purification and/or desalination plantaccording to claim 1 wherein the plate-shaped body (14) has a surfacesmaller than the surface of the basin part (3) and wherein theplate-shaped body (14) is equipped with holes or slots for thecirculation of water from an underside of the plate-shaped body to anupper side thereof.
 5. The water purification and/or desalination plantaccording to claim 1 wherein the light-penetrable material of the roofpart (2) of the evaporator unit (1) is coated with a tear-resistantcoating.
 6. The water purification and/or desalination plant accordingto claim 3 further comprising a solar panel (22) for producing electricpower for the fan (9) and the pump (5).
 7. The water purification and/ordesalination plant according to claim 6 wherein the solar panel produceselectrical power for a condenser (8).